Antireflective silica coatings based on sol-gel technique with controllable pore size, density, and distribution by manipulation of inter-particle interactions using pre-functionalized particles and additives

Abstract

Methods and compositions for forming durable porous low refractive index coatings on substrates are provided. In one embodiment, a method of forming a porous coating on a substrate is provided. The method comprises coating a substrate with a sol-formulation comprising a silane-based binder, silica-based nanoparticles, and an inter-particle interaction modifier for regulating interactions between the silica-based nanoparticles and annealing the coated substrate. Porous coatings formed according to the embodiments described herein demonstrate good optical properties (e.g., a low refractive index) while maintaining good mechanical durability due to the presence of the inter-particle interaction modifier. The inter-particle interaction modifier increases the strength of the particle network countering capillary forces produced during drying to maintain the porosity structure.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]Embodiments of the invention relate generally to methods and compositions for forming porous low refractive index coatings on substrates.[0003]2. Description of the Related Art[0004]Coatings that provide low reflectivity or a high percent transmission over a broad wavelength range of light are desirable in many applications including semiconductor device manufacturing, solar cell manufacturing, glass manufacturing, and energy cell manufacturing. The transmission of light through a material causes the wavelength of the light to change, a process known as refraction, while the frequency remains unchanged thus changing the speed of light in the material. The refractive index of a material is a measure of the speed of light in that material which is generally expressed as a ratio of the speed of light in vacuum relative to that in the material. Low reflectivity coatings generally have an optimized refractive index (n) in be...

AI Technical Summary

Benefits of technology

This patent relates to methods and compositions for creating porous coatings on substrates. The methods involve coating a substrate with a sol-formulation and then drying it to form a gel on the substrate. The sol-formulation contains a silane-based binder, silica-based nanoparticles, and an inter-particle interaction modifier to control interactions between the nanoparticles. The resulting coatings have low refractive indexes and are porous. The sol-formulation can be made by mixing a silane-based binder, an acid or base containing catalyst, silica-based nanoparticles, an alcohol containing solvent, and an inter-particle interaction modifier. The resulting reaction mixture can have a hydrolysis or polycondensation reaction.

Problems solved by technology

Although such antireflective coatings have been generally effective in providing reduced reflectivity over the visible spectrum, the coatings have suffered from deficiencies when used in certain applications.

For example, it is often difficult to control pore size and shape.

Further, porous AR coatings which are used in solar applications are highly susceptible to moisture absorption.

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